using System.Linq;
using System.Text;
using GFramework.SourceGenerators.Common.constants;
using GFramework.SourceGenerators.Common.generator;
using GFramework.SourceGenerators.diagnostics;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp.Syntax;

namespace GFramework.SourceGenerators.rule;

[Generator]
public sealed class ContextAwareGenerator : MetadataAttributeClassGeneratorBase
{
    protected override string AttributeMetadataName =>
        $"{PathContests.SourceGeneratorsAbstractionsPath}.rule.ContextAwareAttribute";

    protected override string AttributeShortNameWithoutSuffix => "ContextAware";

    protected override bool ValidateSymbol(
        SourceProductionContext context,
        Compilation compilation,
        ClassDeclarationSyntax syntax,
        INamedTypeSymbol symbol,
        AttributeData attr)
    {
        var iContextAware = compilation.GetTypeByMetadataName(
            $"{PathContests.CoreAbstractionsNamespace}.rule.IContextAware");

        if (iContextAware is null)
        {
            context.ReportDiagnostic(Diagnostic.Create(
                ContextAwareDiagnostic.ClassMustImplementIContextAware,
                syntax.Identifier.GetLocation(),
                symbol.Name));
            return false;
        }

        if (!symbol.AllInterfaces.Any(i =>
                SymbolEqualityComparer.Default.Equals(i, iContextAware)))
        {
            context.ReportDiagnostic(Diagnostic.Create(
                ContextAwareDiagnostic.ClassMustImplementIContextAware,
                syntax.Identifier.GetLocation(),
                symbol.Name));
            return false;
        }

        return true;
    }

    /// <summary>
    ///     生成源代码
    /// </summary>
    /// <param name="context">源生产上下文</param>
    /// <param name="compilation">编译对象</param>
    /// <param name="symbol">命名类型符号</param>
    /// <param name="attr">属性数据</param>
    /// <returns>生成的源代码字符串</returns>
    protected override string Generate(
        SourceProductionContext context,
        Compilation compilation,
        INamedTypeSymbol symbol,
        AttributeData attr)
    {
        var ns = symbol.ContainingNamespace.IsGlobalNamespace
            ? null
            : symbol.ContainingNamespace.ToDisplayString();
        var iContextAware = compilation.GetTypeByMetadataName(
            $"{PathContests.CoreAbstractionsNamespace}.rule.IContextAware");

        var sb = new StringBuilder();
        sb.AppendLine("// <auto-generated/>");
        sb.AppendLine("#nullable enable");
        sb.AppendLine();

        if (ns is not null)
        {
            sb.AppendLine($"namespace {ns};");
            sb.AppendLine();
        }

        sb.AppendLine($"partial class {symbol.Name}");
        sb.AppendLine("{");

        GenerateContextProperty(sb);
        GenerateInterfaceImplementations(sb, iContextAware!);

        sb.AppendLine("}");
        return sb.ToString().TrimEnd();
    }

    protected override string GetHintName(INamedTypeSymbol symbol)
        => $"{symbol.Name}.ContextAware.g.cs";

    // =========================
    // 生成 Context 属性
    // =========================
    private static void GenerateContextProperty(StringBuilder sb)
    {
        sb.AppendLine("    /// <summary>");
        sb.AppendLine("    /// 自动注入的架构上下文");
        sb.AppendLine("    /// </summary>");
        sb.AppendLine(
            $"    protected {PathContests.CoreAbstractionsNamespace}.architecture.IArchitectureContext Context {{ get; private set; }} = null!;");
        sb.AppendLine();
    }

    // =========================
    // 自动实现接口方法
    // =========================
    private static void GenerateInterfaceImplementations(
        StringBuilder sb,
        INamedTypeSymbol interfaceSymbol)
    {
        var interfaceFullName = interfaceSymbol.ToDisplayString(
            SymbolDisplayFormat.FullyQualifiedFormat);

        foreach (var member in interfaceSymbol.GetMembers().OfType<IMethodSymbol>())
        {
            if (member.MethodKind != MethodKind.Ordinary)
                continue;

            GenerateMethod(sb, interfaceFullName, member);
            sb.AppendLine();
        }
    }

    private static void GenerateMethod(
        StringBuilder sb,
        string interfaceFullName,
        IMethodSymbol method)
    {
        var returnType = method.ReturnType.ToDisplayString(
            SymbolDisplayFormat.FullyQualifiedFormat);

        var parameters = string.Join(", ",
            method.Parameters.Select(p =>
                $"{p.Type.ToDisplayString(SymbolDisplayFormat.FullyQualifiedFormat)} {p.Name}"));

        sb.AppendLine(
            $"    {returnType} {interfaceFullName}.{method.Name}({parameters})");

        sb.AppendLine("    {");
        GenerateMethodBody(sb, method);
        sb.AppendLine("    }");
    }

    // =========================
    // 方法语义策略
    // =========================
    private static void GenerateMethodBody(
        StringBuilder sb,
        IMethodSymbol method)
    {
        switch (method.Name)
        {
            case "SetContext":
                sb.AppendLine("        Context = context;");
                break;

            case "GetContext":
                sb.AppendLine("        return Context;");
                break;

            default:
                GenerateFallbackBody(sb, method);
                break;
        }
    }

    private static void GenerateFallbackBody(
        StringBuilder sb,
        IMethodSymbol method)
    {
        if (method.ReturnsVoid)
        {
            sb.AppendLine("        // no-op");
        }
        else
        {
            sb.AppendLine(
                $"        throw new System.NotImplementedException(");
            sb.AppendLine(
                $"            \"Method '{method.Name}' is not supported by ContextAwareGenerator.\");");
        }
    }
}